If you take the slab away, do the wall trim as you would expect?
It is really hard to say without having the actual model to dissect.
The reference lines of the walls appear to be the same (good), but does the slab extend to that reference line as well?
My guess is the slab is cutting one of the wall (concrete one?) leaving a gap in that, so the concrete wall has nothing to cut the framed wall and the slab is not cutting the framed wall either.
It might just be an issue with building material strengths or it could be the extent of the side of the slab.
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